VOA常速英語(yǔ):經(jīng)歷了1500年冰封以后苔蘚植物重新煥發(fā)生機(jī)

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Antarctica is the coldest, driest and windiest place on Earth, but plants can take root there and survive and a new study finds that moss can come back to life after centuries buried in the permafrost.

Signy Island, off the Antarctic Peninsula, is one of the richest wildlife habitats on the frozen continent. Each summer when the ice retreats, it becomes a refuge for penguins and sea birds, and plants - especially mosses - return to life.

It’s here that Peter Convey, a scientist with the British Antarctic Survey, drills through the newly sprouted moss into the frozen ground to extract cores that will help him reconstruct the Earth’s climate history.

In this study, Convey’s team wanted to know how far back in time - or down the core - the moss retained its ability to regenerate. Earlier research suggested that frozen plant material could be revived after 20 years at most.

“So to look at it, we got a core. We sliced it half down the middle, so lengthways, and put the halves in sterile boxes in a sort of standard growth incubator," Convey said. "And it turned out after about three to four weeks you could see some new growth appearing in parts of the core.”

That regenerated moss dated back 1,500 years. Other studies show that only microbes are capable of revival after so many years. Writing in the Cell Press journal Current Biology, Convey reports seeing plant shoots on the entire length of the 1.5 meter core.

"And you can go further than that if you really want to," he said. "You can look at leaves on the shoot and the leaves are pretty well perfectly preserved down the core as well. So, one of the beauties of this sort of moss core is that you get a live surface, a growing surface. And then as you go down into the core, very quickly it becomes frozen in permafrost.”

The moss survives so long in this deep freeze by building on the tolerance features it developed to flourish in the harsh Antarctic landscape. Convey says that survival mechanism has special relevance now, in the context of climate change, as the polar regions warm faster than any other part of the globe.

“Now if we can imagine the situation where a moss bank like this gets covered over by ice, but the moss is viable in the permafrost underneath the ice, then as the ice recedes, you’ve actually got organisms in place that effectively are ready to go as soon as the ice goes away and their habitat becomes available again," he said. "So you’ve got a means of preserving diversity in the region.”

And, Convey asks, if moss can survive 1,500 years locked away in the permafrost, maybe it can last even longer, through interglacial periods of 10,000 years or more. That's the subject for another study.